163 Int. Arch. Otorhinolaryngol., São Paulo - Brazil, v.17, n.2, p. 163-167, Apr/May/June - 2013. Original Article Int. Arch. Otorhinolaryngol. 2013;17(2):163-167. DOI: 10.7162/S1809-97772013000200008 Effect of fractionated radiotherapy on the parotid gland: an experimental study in Brazilian minipigs Roberta Targa Stramandinoli-Zanicotti 1 , Laurindo Moacir Sassi 2 , Juliana Lucena Schussel 3 , Maria Fernanda Torres 4 , Melissa Funchal 5 , Gustavo Henrique Smaniotto 6 , José Luis Dissenha 7 , Andre Lopes Carvalho 8 . 1) DDS, MSc, PhD student. Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil; Oncology Department, University of São Paulo, São Paulo / SP - Brazil. 2) DDS, PhD. Chief of the Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil. 3) DDS, PhD. Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil. 4) DVM, PhD. Experimental Surgery Department, Positivo University, Curitiba / PR - Brazil; Veterinary Medicine of Federal University of Parana, Curitiba / PR - Brazil. 5) Medical Physics. Radiotherapy Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil. 6) MD. Radiotherapy Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil. 7) DDS. Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil. 8) MD, PhD. Head and Neck Surgery and Otorhinolaryngology Department, Hospital de Cancer de Barretos, Barretos, SP, Brazil; Oncology Department, University of São Paulo, São Paulo / SP - Brazil. Institution: Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital. Curitiba / PR - Brazil. Mailing address: Roberta Targa Stramandinoli-Zanicotti - Hospital Erasto Gaertner - Rua Dr. Ovande do Amaral, 201 - Curitiba / PR - Brazil - Zip-code: 81520-060 - E-mail: [email protected]This research was funded by grants from the Araucaria Foundation (Curitiba, PR, Brazil), the CAPES Foundation (Ministry of Education of Brazil, Brasília, DF, Brazil), and the National Council for Scientific and Technological Development - CNPq (Brasília, DF, Brazil). Article received on September 23, 2012. Article accepted on December 3, 2012. S UMMARY Introduction: Radiotherapy (RT) of head and neck neoplasms often damages the salivary glands. Aim: To examine the pattern of morphologic changes resulting from RT of the head and neck region in minipig parotid glands in a clinical and experimental research setting. Methods: Twelve 18-month-old male Brazilian minipigs weighing 30–40 kg were selected. Eight minipigs were assigned to the experimental group (group 1) and 4 to the control group (group 2). The RT was performed under general anesthesia at Erasto Gaertner Hospital, Curitiba, Brazil, using an á/â ratio of 2.5. The minipigs from group 1 underwent 3 sessions of irradiation with Cobalt 60 of the head and neck, bilaterally, with 3 exposures of 8 Gy each at 7-day intervals for a total dose of 24 Gy. The animals were sacrificed 12 weeks post-RT. Results: The irradiated parotid glands displayed reductions in the size and number of acini as well as loss of secretory granules. The presence of fibrosis and loss of parenchyma relative to non-irradiated glands were observed, with an average reduction in volume of 54%. Conclusions: Our results demonstrate that this model for parotid gland damage resulting from an RT regimen appears to be useful for preclinical large animal studies of RT-induced damage and testing novel potential treatment options. Although recent advances in radiation therapy, such as intensity-modulated radiation therapy, have reduced the dose and limited the field of radiation, considerable salivary gland injury still occurs and can greatly impact the patient’s quality of life after cancer treatment. Keywords: Head and Neck Neoplasms; Radiotherapy; Salivary Glands; Xerostomia; Swine, Miniature. occur after RT include dental caries, dysgeusia, dysphagia, candidiasis, and osteoradionecrosis (2,8,10,13). Radiation- induced damage to the salivary glands includes parenchymal fibrosis and secretory hypofunction that leads to xerostomia. The effects of RT on the salivary glands become apparent shortly after treatment and are directly related to the structural damage (13). Although recent advances in radiation therapy, such as intensity-modulated RT (IMRT), have reduced the dose and limited the field of radiation, considerable salivary gland injury still occurs (5,13). Radiation-induced damage to the salivary gland has I NTRODUCTION Radiotherapy (RT) is an important part of head and neck cancer treatment, either as the primary modality or as an adjuvant treatment (2). The salivary glands are usually included in the field of radiation. The radiation field for RT of nasopharyngeal and oropharyngeal cancers often includes 100% of the parotid gland (13). RT causes acute or early and late toxicities, the severity of which depends on the dose that was required for treatment (2). RT also affects tumor- adjacent tissue, including the mucosa, vasculature, muscle, bone, and salivary glands, and these tissues are also affected by RT-related side effects (3,4,10). The complications that
5
Embed
Effect of fractionated radiotherapy on the parotid gland ... · Radiotherapy (RT) is an important part of head and neck cancer treatment, either as the primary modality or as an adjuvant
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
163
Int. Arch. Otorhinolaryngol., São Paulo - Brazil, v.17, n.2, p. 163-167, Apr/May/June - 2013.
Original Article Int. Arch. Otorhinolaryngol. 2013;17(2):163-167.
DOI: 10.7162/S1809-97772013000200008
Effect of fractionated radiotherapy on the parotid gland: an experimentalstudy in Brazilian minipigs
Roberta Targa Stramandinoli-Zanicotti1, Laurindo Moacir Sassi2, Juliana Lucena Schussel3, Maria Fernanda Torres4,Melissa Funchal5, Gustavo Henrique Smaniotto6, José Luis Dissenha7, Andre Lopes Carvalho8.
1) DDS, MSc, PhD student. Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil; Oncology Department, University of São Paulo,São Paulo / SP - Brazil.
2) DDS, PhD. Chief of the Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil.3) DDS, PhD. Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil.4) DVM, PhD. Experimental Surgery Department, Positivo University, Curitiba / PR - Brazil; Veterinary Medicine of Federal University of Parana, Curitiba / PR - Brazil.5) Medical Physics. Radiotherapy Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil.6) MD. Radiotherapy Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil.7) DDS. Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital, Curitiba / PR - Brazil.8) MD, PhD. Head and Neck Surgery and Otorhinolaryngology Department, Hospital de Cancer de Barretos, Barretos, SP, Brazil; Oncology Department, University of
São Paulo, São Paulo / SP - Brazil.
Institution: Oral and Maxillofacial Surgery Department, Erasto Gaertner Hospital.Curitiba / PR - Brazil.
Mailing address: Roberta Targa Stramandinoli-Zanicotti - Hospital Erasto Gaertner - Rua Dr. Ovande do Amaral, 201 - Curitiba / PR - Brazil - Zip-code: 81520-060 -E-mail: [email protected] research was funded by grants from the Araucaria Foundation (Curitiba, PR, Brazil), the CAPES Foundation (Ministry of Education of Brazil, Brasília, DF, Brazil), andthe National Council for Scientific and Technological Development - CNPq (Brasília, DF, Brazil).Article received on September 23, 2012. Article accepted on December 3, 2012.
SUMMARY
Introduction: Radiotherapy (RT) of head and neck neoplasms often damages the salivary glands.
Aim: To examine the pattern of morphologic changes resulting from RT of the head and neck region in minipig parotid glands
in a clinical and experimental research setting.
Methods: Twelve 18-month-old male Brazilian minipigs weighing 30–40 kg were selected. Eight minipigs were assigned to the
experimental group (group 1) and 4 to the control group (group 2). The RT was performed under general anesthesia at Erasto
Gaertner Hospital, Curitiba, Brazil, using an á/â ratio of 2.5. The minipigs from group 1 underwent 3 sessions of irradiation with
Cobalt 60 of the head and neck, bilaterally, with 3 exposures of 8 Gy each at 7-day intervals for a total dose of 24 Gy. The animals
were sacrificed 12 weeks post-RT.
Results: The irradiated parotid glands displayed reductions in the size and number of acini as well as loss of secretory granules.
The presence of fibrosis and loss of parenchyma relative to non-irradiated glands were observed, with an average reduction
in volume of 54%.
Conclusions: Our results demonstrate that this model for parotid gland damage resulting from an RT regimen appears to be
useful for preclinical large animal studies of RT-induced damage and testing novel potential treatment options. Although recent
advances in radiation therapy, such as intensity-modulated radiation therapy, have reduced the dose and limited the field of
radiation, considerable salivary gland injury still occurs and can greatly impact the patient’s quality of life after cancer treatment.
Keywords: Head and Neck Neoplasms; Radiotherapy; Salivary Glands; Xerostomia; Swine, Miniature.
occur after RT include dental caries, dysgeusia, dysphagia,
candidiasis, and osteoradionecrosis (2,8,10,13). Radiation-
induced damage to the salivary glands includes parenchymal
fibrosis and secretory hypofunction that leads to xerostomia.
The effects of RT on the salivary glands become apparent
shortly after treatment and are directly related to the
structural damage (13).
Although recent advances in radiation therapy, such
as intensity-modulated RT (IMRT), have reduced the dose
and limited the field of radiation, considerable salivary
gland injury still occurs (5,13).
Radiation-induced damage to the salivary gland has
INTRODUCTION
Radiotherapy (RT) is an important part of head and
neck cancer treatment, either as the primary modality or as
an adjuvant treatment (2). The salivary glands are usually
included in the field of radiation. The radiation field for RT
of nasopharyngeal and oropharyngeal cancers often includes
100% of the parotid gland (13). RT causes acute or early and
late toxicities, the severity of which depends on the dose
that was required for treatment (2). RT also affects tumor-
adjacent tissue, including the mucosa, vasculature, muscle,
bone, and salivary glands, and these tissues are also affected
by RT-related side effects (3,4,10). The complications that
164
been studied in many animal models, including the rabbit,
monkey, rat, and miniature pig (minipig) (1,6,8,11-16,18).
Development of an animal model for radiation-related
salivary gland damage using a human RT protocol may
assist further investigations on preventing or minimizing
such adverse effects and preserve salivary gland function
(13). Minipig parotid glands share many anatomic and
physiologic characteristics with human glands (20), including
the volume and diameter of the main excretory duct.
Previous studies have suggested that this animal model is
suitable for functional and structural studies of the salivary
gland (9,13).
A previous experimental study (6) investigated the
histological changes induced by radiation therapy in the
submandibular gland of rats. The animals were subjected to
doses of 10 and 15 Gy and sacrificed 16 or 21 days after the
RT. Histological examination with hematoxylin and eosin
(HE) staining revealed changes in the size, shape, and
pigmentation of the nuclei of the acinar cells. Another
study evaluated the the early and late effects of radiation
on the salivary glands of rats (12) and observed tissue loss
and dysfunction of the salivary glands until 1 year post-
radiotherapy. The radiation-induced injury was delayed in
both the parotid and submandibular glands but was more
evident in the first.
An experimental study conducted in India, in which
pigs were subjected to daily fractionated irradiation totaling
70 Gy and sacrificed 30 days after the completion of RT,
showed significant loss of lung parenchyma, with severe
acinar atrophy and interstitial fibrosis, enlargement of the
nuclei in the remaining acinar cells, and ductal proliferation
and dilatation in the irradiated group. No pathological
changes were observed in the parotid and submandibular
glands of the control group.
Histological analysis of the changes induced by
radiotherapy of the salivary glands in experimental studies
is important for clinical management and treatment of
patients who need RT of the head and neck. The aim of this
study was to examine the morphologic changes to minipig
parotid glands resulting from fractionated RT of the head
and neck region.
MATERIALS AND METHODS
Animals
Eight 18-month-old male Brazilian minipigs (Minipig
Br1, Minipig Pesquisa & Desenvolvimento, São Paulo,
Brazil) weighing 30–40 kg were used in this study. The
study was reviewed and approved by The Animal Research
Ethics Committee of the Positivo University, Curitiba, PR,
Brazil (001/2009). All minipigs were housed together with
free access to food and water. Four minipigs were assigned
to the experimental group (group 1) and 4 to the control
group (group 2).
Irradiation protocol
The radiotherapy was performed under general
anesthesia at Erasto Gaertner Hospital, Curitiba, PR, Brazil.
The minipigs from group 1 underwent 3 sessions of irradiation
with Cobalt 60 (Theratron 780C - MDS Nordion, Ontario,
Canada) of the head and neck, bilaterally, with 3 exposures
of 8 Gy each at 7-day intervals for a total dose of 24 Gy. To
ensure that the location of the radiation was correct, a face
mask was made from thermoplastic material (Rolyan Aquaplast
Splinting Materials, Sammons Preston, Illinois, USA) and used
during the RT (Figure 1). Assuming an á/â ratio of 2.5, this
dose is biologically equivalent to approximately 56 Gy, or 28
exposures of 2 Gy each (17). The animals in the control
group were not irradiated at any time.
Salivary gland histologic evaluation
The animals from group 1 were sacrificed 12 weeks
post-RT. The parotid glands on both sides were dissected
from animals from both groups and their macroscopic
features analyzed. The specimens were fixed in 10%
formalin, embedded in paraffin, and sectioned at a thickness
of 5 μm for hematoxylin and eosin (HE) staining. The
specimens were examined using a light microscope at 10
to 40 magnification by a single pathologist who analyzed
all of the specimens. For each section, 5 fields were
selected randomly for quantitative histopathologic
assessment of the acinar secretory and ductal tissues. The
features analyzed were fibrosis, acinar atrophy, parenchymal
loss, striated duct dilation, and intercalated duct proliferation
and dilation.
Oral tissue evaluation
The other oral structures that were within the
irradiated area, such as the tongue, gingiva, and lip vermillion,
were also dissected, fixed in 10% formalin, embedded in
paraffin, sectioned at a thickness of 5 μm for HE staining,
and analyzed by light microscopy. The aim was to compare
non-irradiated and irradiated structures and search for
changes induced by irradiation. The same groups of animals
were used, and the histological analysis evaluated basophilic
degeneration, blood vessels, inflammatory infiltrates, and
submucosa structures such as the minor salivary glands and
muscle tissue.
Effect of fractionated radiotherapy on the parotid gland: an experimental study in Brazilian minipigs. Stramandinoli-Zanicotti et al.
Int. Arch. Otorhinolaryngol., São Paulo - Brazil, v.17, n.2, p. 163-167, Apr/May/June - 2013.
165
RESULTS
Irradiated glands
The irradiated and non-irradiated parotid glands
were macroscopically different in size and volume (Table
1, Figure 2).
The irradiated parotid glands showed reductions in
the size and number of acini, loss of eosinophilic staining
in the cytoplasm, and loss of secretory granules. Most cells
also exhibited prominent, enlarged, hyperchromatic nuclei.
Fibrosis and loss of parenchyma relative to non-irradiated
glands could be observed. Significant ductal changes were
evident, the most common of which was ductal dilation
that was sometimes accompanied by cellular debris and
occasional microliths. A mononuclear inflammatory infiltrate
with scattered neutrophils was also present (Figure 3).
All irradiated animals remained generally healthy,
appeared to eat well, and exhibited no malaise or other
clinically significant adverse reaction to RT except for
alopecia in the mandibular region.
DISCUSSION
Radiation is an important tool for both curative and
palliative treatment of head and neck cancer. However,
despite the beneficial effects of RT on tumor control, the
radiation dose to the adjacent normal tissue may cause
complications (19). RT for head and neck cancer usually
affects the salivary glands, resulting in loss of gland
function with reduction in saliva flow and xerostomia as
early complications. The loss of saliva flow is a potentially
debilitating condition that can permanently compromise
oral health and nutrition (13). Radiation-induced xerostomia
Figure 1. Experimental radiotherapy of the head and neck
region in BR-1 Minipigs. A thermoplastic face mask was used
for animal immobilization during the radiotherapy sessions.
Figure 2. Characterization of the parotid gland after experi-
mental radiotherapy in BR-1 Minipigs: (A) non-irradiated
gland and (B) irradiated gland.
Figure 3. Histological sections of parotid glands from BR-1
Minipigs. (A) Normal parotid gland and (B) Parotid gland after
irradiation showing acinar atrophy. (Hematoxylin and eosin,
10).
Table 1. Mensuration of irradiated and non-irradiated parotid glands from BR-1 Minipigs.
Sample Right Gland Volume Left Gland Volume Average